The use of adsorbents is recommended whenever particular substances are to be removed from a mixture. Among the adsorbents, active carbon enjoys a special position which can be attributed to its high adsorption capacity due to its very great internal surface and its relatively unspecific adsorption, i.e., its physical adsorption. Furthermore, active carbon can be adapted to a particular application through the selection of its source material and the manner in which it is activated.
One important application of active carbon is in pliable filter sheet materials which are used in industry, in the household, but particularly in protective clothing. They consist usually of a support, which is often a textile material, on which a mixture of binding agent and adsorbent is applied by immersing it and squeezing out the excess. The binder is the cause of a reduction of the adsorption capacity, and in the case of textile materials, it always causes unwanted alterations in the pliability of the fabric due to cementing of the threads, which is a handicap especially in connection with garments (protective clothing).
The invention is addressed to the problem of creating filter sheet materials from an air-permeable, pliable, especially textile, support material, and an adsorbent fixed thereon, in which the special selection of the adsorber particles and their anchoring on the support material will be such as to assure not only optimum adsorption properties, but also high pliancy, good resistance to rub-off, and high air-permeability.
The quantity of the adsorber particles is to be uniformly distributed so as to achieve a uniform filtering action with a minimum of stray and accordingly good protective action combined with minimum rub-off. Moreover, the improved filter material is to be nonbulky, and must be washable without quality losses.